1. Field of the Invention
The present invention relates to a car door mirror and more particularly to a set plate for rotatably supporting a door mirror body that stores a mirror plate.
2. Related Art Statement
In accordance with recent demands for weight saving of a car body and cost saving, various metal parts have been replaced by synthetic resins. A door mirror is not an exception. Synthetic resins are extensively used for not only the door mirror body, but also a set plate that supports the door mirror body. The set plate comprises a base plate to be attached to a car door and a support shaft for rotatably supporting the door mirror body. The set plate is conventionally made of zinc die cast metal. If the base plate and the support shaft are integrally molded out of synthetic resin, this would enable a drastic reduction in weight compared to a metal set plate.
With regard to using a synthetic resin for the set plate as a supporting member for the door mirror body, there have been the following problems. Firstly, if the support shaft as well as the set plate is made of synthetic resin, the base of the support shaft produces insufficient strength. While the stress concentrates on the base of the support shaft, the synthetic resin lacks the member strength against the stress concentration. In order to relieve the stress concentration, a curved surface section is generally provided at the bottom of the support shaft. However, increasing the diameter of the support shaft is undesirable because of limitations on the set plate size and relation with the other parts. For this reason, it has been difficult to form the curved surface section for relieving the stress at the support shaft base and has caused insufficient strength to the support shaft.
Secondly, a thrust washer attached to the support shaft base causes the following problem. The support shaft base is attached with the thrust washer that is arranged between the base plate and the door mirror body for supporting the door mirror body. If the support shaft base is provided with the curved surface section, however, the thrust washer cannot be placed on a flat surface, preventing smooth rotations of the door mirror body. If the thrust washer is arranged so as to avoid the curved surface section, a large play is caused between the washer and the support shaft. The washer may deviate and cover the curved surface section. Further, the washer diameter increases for the play, disadvantageous to space saving considerations.
Thirdly, there is also the problem of insufficient strength concerning a mechanism to restrict operations of the door mirror body. The set plate also provides such functions as restricting a rotational range of the door mirror body and setting a retracted position and a neutral position (working position). A conventional set plate realizes the former function by engaging a groove provided on the door mirror body with a stopper protrusion formed on the set plate and allowing rotative movement of the door mirror body for an angle to form the groove. The latter function is realized by providing a steel ball on the door mirror body and engaging it with a cavity formed at a specified location on the set plate.
The set plate, if made of synthetic resin, causes insufficient strength to the stopper protrusion that touches the groove end and restricts rotative movement of the door mirror body. The stopper protrusion and the steel ball are configured completely different although they are both associated with rotational angles of the door mirror body. There has also been a problem of complicating parts shapes and degrading the space saving efficiency.
The conventional set plate also has a problem with positioning of a conducting wire to be inserted into the support shaft. The support shaft for the set plate has a hollow inside into which the conducting wire is inserted to supply power to a motor and the like for the door mirror body. Since the conventional set plate uses a same hollow inside the support shaft, however, it is difficult to determine how long the conducting wire is inserted. In this case, a worker determines the amount of insertion by his or her visual inspection and experience. The accuracy easily fluctuates depending on workers.